Process for making printing plates



United. States Patent 3,490,905 PROCESS FOR MAKING PRINTING PLATES Ralph Kingsley Blake, Westfield, N.J., assignor to E. I. du Pont de Nemours and Company, Wilmington, Del., a corporation of Delaware No Drawing. Filed Oct. 6, 1964, Ser. No. 401,971 Int. Cl. G03c 5/54; G03f 7/06 US. Cl. 96--29 11 Claims ABSTRACT OF THE DISCLOSURE Process for making inked printing plates which comprises (a) forming by silver transfer development, using hydroquinone or 2,4-diaminophenol or a mixture of either of them with l-phenyl-3-pyrazolidone, l-phenyl-4-methyl-3-pyrazolidone or 1-methy1amino-4-hy1 droxybenzene and a silver halide solvent, a silver surface image in an outer water-permeable layer of an exposed colloidal silver halide layer;

(b) treating the surface of said layer (1) with an aqueous solution and (2) with a printing ink containin oleophilic binding agent; and

(c) using said plates to print.

This invention relates to a lithographic printing process and, more specifically, to a photographic method for the preparation of lithographic printing plates.

Various photographic methods are employed in the lithographic art for the formation of an oleophilic, that is, greasy ink loving, image on an oleophobic, that is, greasy ink repellent, surface of a lithographic printing plate. In photographic methods a negative is usually produced by photographing the original. Subsequently the lithographic plate, in which the lithographic surface has been presensitized with a material such as a resin-forming diazo compound or with a dichromate compound capable of tanning a colloid when exposed to light, is exposed to light through the negative whereby the exposed areas are converted to an oleophilic image which accepts the ink and prints from these areas. The light sensitive materials remaining in the unexposed portions of the plate, or the non-imaged areas is removed, e.g., by washing, to provide an oleophobic surface in the non-image areas. Such plates may be mounted on a roller of an offset printing press, for example, passed in contact with an aqueous fountain solution and a printing ink. The inked image is then transferred to a blanket, and applied to the sheet to be printed.

It is an object of this invention to readily provide lithographic printing plates. Another object of this invention is to obtain lithographic printing masters, which may have negative or positive metallic silver surface images depending upon the imaging technique utilized, rapidly from photographic elements having water-permeable colloid silver halide emulsion layers. A further object of this invention is to obtain by photographic imaging techniques an oleophilic silver image on the surface of the unexposed areas of the photographic element which can be used as a lithographic printing plate yielding" positive copies thus eliminating the need for preparing a negative film as an intermediate.

Other objects of this invention will be apparent from the following description of the invention.

Before describing the invention in detail, a positive copy is defined herein as an ink image on the copy sheet corresponding to the original while a negative? copy is defined herein as an inked background on the copy sheet with the image not being inked.

The process of this invention constitutes a simple, effective, convenient and versatile process for forming an inked 3,490,905 Patented Jan. 20, 1970 planographic printing plate directly from an exposed photographic element having a colloid silver halide emulsion layer.

The process for photographically forming the positive printing elements of this invention in its broader aspects comprises (a) Forming by silver transfer development a metallic silver surface image in the unexposed areas of an outer Water-permeable colloid layer of a photographic film element having an exposed colloid silver halide emulsion layer, and

(b) Treating the surface of the positive image-bearing layer with an aqueous fountain solution and then with a printing ink having an oleophilic binding agent, whereby said ink adheres to the areas of the surface that corresponds to the metallic silver surface image. The silver image formed by step (a) can be negative or positive preferably the latter. The resulting inked planographic printing plate can then be used onto any suitable desired surface to make copies. The plate can be inked repeatedly to make the desired number of copies.

In the process, the silver halide emulsion layer may be outermost, in which case the silver surface image is present on and/ or near the surface of such layer. However, if a gelatin antiabrasion layer is present, the silver surface image will be formed in that layer.

When a light-sensitive element, e.g., a gelatino-silver halide film, is photographically exposed and developed with conventional developers containing small concentrations of a silver halide solvent, the surface of the exposed areas of the element are made relatively oleophilic in comparison to the unexposed surface area. However, if in accordance with this invention, a silver halide solvent is used in higher concentrations and a nucleating agent is added to these conventional developers, silver transfer takes place in the unexposed areas and a silver image is formed in the layer in these areas. If the developer is too slow in its action, the surface silver image will not form and, accordingly, developer solutions containing two developing agents are preferred.

Preference for a two-developing agent solution containing the silver halide solvent and silver nucleating agent specified is emphasized in the case of fslow developing photographic film. A silver-bromideiodide X-ray type film is a slow developing film. In the development of that type of film, a twodeveloping agent solution may be advantageous.- It is also advantageous to increase the pH of the solution, which in itself increases the developing rate.

The silver halide may be silver chloride, silver bromide or mixtures of silver chloride and bromide. Minor amounts of silver iodide may also be present in such silver halide emulsions.

To obtain good prints it is necessary that the different oleophilic and oleophobic properties of the image andthe background surface be sufiiciently great that when water and ink are applied, the image will accept sufficient ink without the background accepting any ink at all. Hence, lithographic plates usually have a base surface which accepts Water but repels greasy printing inks.

In this invention, the silver halide emulsion layer is preferably overcoated with a transparent receptive layer, which constitutes an antiabrasion layer, and is normally a gelatin layer. It is into this layer that the nucleating agent will permeate to allow the silver image to form. The receptive layer must be a hardened non-removable colloid layer which is permeable to water. The receptive layer is nucleated after exposure via the developing solution during processing. Some films contains silica in this gelatin overcoating, known as the antiabrasion layer. While the presence of silica in this layer may improve the process, the silica is not essential to the process. The

light-sensitive element does not have to have an antiabrasion layer as the silver surface image will form on and/or in the top of the emulsion in the absence of an antiabrasion layer.

In the unexposed areas during development, it is believed that the silver ions migrate to or near the surface of the light-sensitive element as a complex ion. The nucleating agents, having permeated the surface region, are the starting points for reduction of the silver ion complex to metallic silver.

The nucleating agent must be capable of diffusing into the antiabrasion layer or the top of the emulsion layer if there is no antiabrasion layer. Examples of such a useful nucleating agent are sodium sulfide, sodium thiocyanate and thiourea. The concentration of the nucleating agent in the developer solution varies with the type of developer and with the type of light-sensitive element being used in this process. The operable concentrations can be determined readily in each case by relatively simple laboraory techniques, and optimum concentrations can be determined in the same manner, the nucleating agent to be present in an amount of 50 to 3000 mg. per liter. In the case of water-soluble thiocyanates the nucleating agent may be present in an amount of to 1800 mg. per liter.

Preferred silver halide solvents include sodium, ammonium and potassium thiosulfates in amounts from 4 to 35 gm. of thiosulfate ion per liter of solution, sodium, ammonium and potassium thiocyanate in amounts from 7 to 90 gm. of thiocyanate ion per liter of solu tion, and sodium, ammonium and potassium sulfite in amounts from 50 gm. of sulfite ion per liter of solution to the amount necessary for a saturated solution.

When a two-agent developer solution is used even in a two-bath developer set-up, containing a nucleating agent and a silver halide solvent, normally a printing plate will be obtained which produces positive copies. The preferred embodiment would consist of the first agent being chosen from the group consisting of l-phenyl 3-pyrazolid-one, 1 phenyl 4-methyl-3-pyrazolidone, and p-methylaminophenol sulfate, and a second agent being chosen from the group consisting of hydroquinone and 2,4-diaminophenol. If a two-bath developer is used, two different sets of agents can be used in the two baths. A combination of two agents of the types specified allows the tanning rates and the silver transfer to form a balance of the surface properties which makes the unexposed surface area oleophilic in relation to the exposed surface area, hence, positive copies can be made.

In Examples 14, 15, 16 and 17, routes not already elaborated upon are presented.

The following examples illustrate this invention but are not intended to limit it in any way.

EXAMPLE 1 A developer solution was prepared as follows: Water ml 800 Sodium sulfite (anhydrous) gm 80 Hydroquinone (anhydrous) gm 16 1 phenyl 4 methyl 3 pyrazolidone (reagent grade) gm 1 Boric acid (H BO gm 5.5 Potassium bromide (anhydrous) gm 2 6-nitrobenzimidazole nitrate (one gram dissolved in sufficient ethanol to make up 100 ml. of solution) ml 40 Sodium hydroxide (24 grams dissolved in sufiicient water to make up 100 ml. of solution) ml 100 Water to make up to 1000 ml. Potassium thiocyanate (100 grams dissolved in 100 ml. water to make up 154 ml. of solution) ml 30 Sodium sulfide (0.1 molar solution) ml 10 A photographic film of the lithographic type was exposed at a distance of 26 inches for seconds to a highintensi y inc nde c nt la p G neral E ectric Photoflood lamp) operated at 13 volts. Exposure was to a positive having a density of 1.4. The film comprised a high contrast silver chloride-silver bromide orthochromatically sensitized emulsion, in which the silver salt contained 20 mole percent silver bromide and mole percent silver chloride, and containing grams of gelatin per mole of silver halide, overcoated with a clear hardened gelatin layer, containing silica particles. The film had a gelatin antihalation backing. The exposed film was immersed for one minute in the monobath developer solution and then washed with water. A high contrast, highly reflective, positive silver image was obtained on and/or in the antiabrasion surface coating on the emulsion layer. This developed film constituted a printing plate. The film strip was wetted with 5% aqueous acetic acid. A conventional greasy lithographic ink was applied to a printers hard rubber roller and the roller was used to apply ink to the film strip until ink appeared to adhere imagewise to the strip. A white piece of paper was placed on the inked side of the strip, pressed smooth, and removed. After several treatments, several positive copies were obtained.

EXAMPLE 2 The first bath solution of a developer consisting of solutions A and B was prepared as follows:

Solution A- Water ml 1600 Sodium sulfite (anhydrous) gm Hydroquinone (anhydrous) gm 32 Boric acid (H BO gm 11 Sodium hydroxide (24 grams dissolved in sufficient water to make up 100 ml. of solution ml 200 'Resorcinol (reagent grade) gm 10 1 phenyl 4 methy1-3-pyrazolidone (reagent grade) gm 2 6-nitrobenzimidazole nitrate (0.5 gram dissolved in a solution containing 50 ml. ethanol and 50 m1. of water) ml 80 Water to make up to 2000 ml.

The second bath solution was prepared as follows:

Solution B-- Water ml 1600 Sodium sulfite (anhydrous) gm 160 Hydroquinone (anhydrous) gm 32 Boric acid (H BO gm 11 Sodium hydroxide (24 grams dissolved in sutficient water to make up to 100 ml. of solution) ml 200 1 phenyl 4 methyl-'3-pyrazolidone (reagent grade) m 2 6-nitrobenzimidazole nitrate (reagent grade) ml 80 Sodium sulfide (0.1 molar solution) ml 20 Potassium thiocyanate (anhydrous) gm.. 60

Water to make up to 2000 ml.

A light-sensitive photographic lithographic film as described in Example 1 was exposed at a distance of 26 inches for 25 seconds to a #2 General Electric Photoflood lamp operated at 13 volts. Exposure was to a positive having a density of 1.4. The exposed film was immersed in solution A for one minute and then in solution B for one minute. A five minute wash with water followed the second immersion. A high contrast, highly reflective, positive silver image was obtained on and/or in the antiabrasion surface coating of the emulsion layer. This developed film constituted a printing plate. The film was placed on a conventional offset duplicating press. The plate, i.e., the film, was rubbed with a 5% solution of acetic acid. The press was started up, and, after a few copies, about 4000 positive copies were obtained.

EXAMPLE 3 :A developer solution was prepared as follows:

Water ml 3200 Sodium sulfite (anhydrous) gm 320 l-methylamino-4-hydroxybenzene sulfate (reagent grade) gm 48 2,4-diaminophenol (reagent grade) gm 37.5 Boric acid (H B0 gm 22 Sodium hydroxide (24 grams dissolved in suflicient water to make up 100 ml. of solution) ml 100 6-nitrobenzimidazole nitrate (0.5 gram dissolved in a solution containing 50 ml. of ethanol and 50 ml.

of water) ml 160 Potassium thiocyanate (anhydrous) gm 120 Water to make up to 4000 ml.

A photographic film of the lithographic type as described in Example 1 was exposed at a distance of 23 inches to #2 General Electric Photofiood lamp operated at 13 volts; one portion of the film was exposed for 15 seconds, a second portion for seconds and a third portion for seconds. Exposure was to a negative having a density of 1.4. The exposed film was immersed for two minutes in the monobath developer solution and then washed for five minutes with water. A high contrast, highly reflective, positive silver image was obtained on and/ or in the antiabrasion surface coating of the emulsion layer. This developed film constituted a printing plate. The plate was treated with acetic acid and ink, as described in Example 1 and then was treated with an organic solvent for the ink, called herein cleaner. The ink and acetic acid step, and the cleaning step were repeated several times. Several positive copies were obtained thereafter when the plate was used. The best copies resulted from the area exposed for 20 seconds.

EXAMPLE 4 A developer consisting of two bath solutions was pre- 6-nitrobenzimidazole nitrate (0.5 gram dissolved in a solution containing 50 ml. of ethanol and 50 ml.

of water) ml 160 The solution was divided into two equal portions by volume. Water was added to the first equal portion to make up 2000 ml. of solution, thereby preparing the first bath solution. The second bath solution was prepared by taking the other equal portion, adding 20 ml. of 0.1 molar sodium sulfide solution and 20 grams of potassium thiocyanate (anhydrous), and then adding enough water to make up 2000 ml. of solution. This was the second bath solution.

A photographic film of the lithographic type as described in Example 1 was exposed at a distance of 24 inches for 25 seconds to a #2 General Electric Photoflood lamp operated at 13 volts. Exposure was to a positive having a density of 1.4. The exposed film was immersed for second in the first bath, and then washed with water for two minutes. Following this, the film was immersed in the second bath for 30 seconds and then washed with water for five minutes. A high contrast, highly reflective, positive silver image was obtained on and/ or in the antiabrasion surface coating of the emulsion layer. After several successive treatments with aqueous acetic acid, ink and cleaner, as described in Example 3, several positive copies were obtained.

EXAMPLE 5 A developer solution was prepared as follows:

Water ml 1600 Sodium sulfite (anhydrous) gm Hydroquinone (anhydrous) gm 22 Potassium carbonate (anhydrous) gm 40 Sodium hydroxide (12 grams dissolved in suflicient water to make up ml. of solution) m1 200 1 phenyl 4 methyl 3 pyrazolidone (reagent grade) gm 2 6-nitrobenzimidazole nitrate (1 gram dissolved in suflicient ethanol to make up 100 ml. of solution) ml 20 Potassium thiocyanate (100 grams dissolved in sufficient water to make up to 154 ml. of solution) ml 48 Thiourea (0.1 molar solution) m1 8 Water to make up to 2000 ml.

A photographic film of the lithographic type as described in Example 1 was exposed in a camera through the base of the film so that there was lateral image reversal. The exposed film was immersed for one minute in the monobath developer and then washed for five minutes with water. A high contrast, highly reflective, positive silver image was obtained on and/or in the antiabrasion surface coating of the emulsion layer. This developed film constituted a printing plate. The film was placed on a conventional offset duplicating press. The plate, i.e., the film, was rubbed with a 5% solution of acetic acid. The press was started up and, after a few copies, about 4000 positive copies were obtained.

'EXAMPLE 6 The first bath solution of a two-bath developer was prepared as follows:

Sodium thiosulfate (40 grams dissolved in suflicient water to make up 100 ml. of solution) Water to make up to 1000 ml.

A light-sensitive photographic film of lithographic type as described in Example 1 was exposed at a distance of 24 inches for 20 seconds to a No. 2 General Electric Photofiood lamp operated at 17 volts A.C. Exposure was to a positive having a density of 1.4. The exposed film was immersed for one minute in the first bath solution and washed for 15 seconds with water; immersed in the second bath for 30 seconds and washed for 15 seconds with water; immersed again for one minute in the first bath and washed for three minutes with water. A high contrast, highly reflective, positive silver image was obtained on and/or in the antiabrasion surface coating of the emulsion layer. This developed film constituted a printing plate. Several positive copies were obtained when the film was used as a printing plate.

7 EXAMPLE 7 A monobath developer was prepared as follows:

6-nitrobenzimidazole nitrate (1 gram dissolved in suflicient ethanol to make up 100 ml. solution) ml Sodium selenide (0.1 molar solution) ml 8 Potassium thiocyanate (100 grams dissolved in 100 ml. water to make up 154 ml. of solution) ml Water to make up to 1000 ml.

A photographic film of the lithographic type as described in Example 1 was exposed at a distance of 24 inches for seconds to a No. 2 General Electric Photoflood lamp operated at 17 volts. Exposure was to a positive having a density of 1.4. The exposed film was immersed for one minute in the monobath developer solution and then washed for three minutes with water. A high contrast, highly reflective, positive silver image was obtained on and/ or in the antiabrasion surface coating of the emulsion layer. This developed film constituted a printing plate. After several successive treatments with acetic acid, ink and cleaner, as described in Example 3, several positive copies were obtained.

EXAMPLE 8 A light-sensitive photographic lithographic film as described in Example 1 was exposed in a camera through the base of the film so that there was lateral image reversal. The first bath solution of the developer was the same as the monobath described in Example 1 minus the potassium thiocyanate and sodium sulfide. The second bath solution was the same at the monobath solution described in Example 1 including the potassium thiocyanate and sodium sulfide. The exposed film was immersed for one minute in the first bath and then washed With water for two minutes. Following this, the film Was immersed in the second bath for one minute and then washed in water. A high contrast, highly reflective, posi tive silver image was obtained on and/or in the antiabrasion surface coating of the emulsion layer. This developed film constituted a printing plate. After several successive treatments with acetic acid, ink, and cleaner, as described in Example 3, several positive copies were obtained.

EXAMPLE 9 A developer solution was prepared with an identical composition of that monobath developer prepared in Example 3 except that there was an addition in this example of six grams of sodium hydroxide per liter of the developing solution.

A light-sensitive photographic X-ray film was exposed at a distance of 24 inches for 20 seconds to a #2 General Electric Photoflood lamp operated at 15 volts. Exposure was to a negative having a density of 1.4. The film was comprised of a high speed bromoiodide emulsion, in which the silver salt contained approximately 1.5 mole percent silver iodide and 98.5 mole percent silver bromide and containing 200 gm. of gelatin per mole of silver halide, coated on both sides of a polyester base with the emulsion being overcoated with an antiabrasion layer. The exposed film was immersed for one minute in the monobath developer solution and then washed for three minutes with water. A high contrast, highly reflective, positive silver image was obtained on and/or in the antiabrasion surface coating facing the exposure light. This developed film constituted a printing plate. After several successive treatments with acetic acid, ink, and cleaner, as described in Example 3, several positive copies were obtained.

EXAMPLE 10 A monobath developer was prepared as follows:

Water ml 1600 Sodium sulfite (anhydrous) gm 160 Hydroquinone (anhydrous) gm 32 Boric acid (H BO gm 11 Sodium hydroxide (24 grams dissolved in sufficient water to make up ml. of solu- Water to make up to 2000 ml.

A light-sensitive photographic lithographic film as described in Example 1 was exposed at a distance of 25 inches for 20 seconds to a #2 General Electric Photoflood lamp operated at volts. The exposure was made to a positive having a density of 1.4. The exposed film was immersed for one minute in the monobath developer solution and then washed for three minutes with Water. A high contrast, highly reflective, positive silver image was obtained on and/or in the antiabrasion surface coating of the emulsion layer. This developed film constituted a printing plate. After several successive treatments with acetic acid, ink, and cleaner, as described in Example 3, several positive copies were obtained.

EXAMPLE 11 The first bath solution of a two-bath developer was prepared as follows:

Water to make up to 2000 ml.

The second bath solution was identical to the monobath developer solution described in Example 10.

A light-sensitive photographic lithographic film as described in Example 1 was exposed at a distance of 25 inches for 20 seconds to a #2 General Electric Photoflood lamp operated at 17 volts. Exposure was to a positive having a density of 1.4. The exposed film was immersed for four minutes in the first bath solution and then washed for 30 seconds with Water. The strip was immersed for one minute in the second bath solution and then washed for three minutes. A high contrast, highly reflective, positive silver image was obtained on and/or in the antiabrasion surface coating of the emulsion layer. This developed film constituted a printing plate. After several successive treatments with the acetic acid, ink, and cleaner, as described in Example 3, several positive copies were obtained.

EXAMPLE 12 A monobath developer was prepared as follows:

Water ml 1600 Sodium sulfite (anhydrous) gm 160 2,4-diaminophenol (reagent grade) gm 36 Boric acid (H BO gm 11 6-nitrobenzimidazole nitrate (one gram dissolved in sufiicient ethanol to make up 100 ml. of

solution) ml 80 Sodium sulfide (0.1 molar solution) ml 20 Potassium thiocyanate (anhydrous) gm 60 A light-sensitive photographic lithographic film as described in Example 1 Was exposed at a distance of 24 inches for ten minutes to a #2 General Electric Photofiood lamp operated at 17 volts. Exposure was to a positive having a density of 1.4. The exposed film was immersed for one minute in the monobath developer solution and then washed for three minutes with water. A high contrast, highly reflective positive silver image was obtained on and/or in the antiabrasion surface coating of the emulsion layer. This developed film constituted a printing plate. After several successive treatments with acetic acid, ink, and cleaner, as described in Example 3, several positive copies were obtained.

EXAMPLE 13 A developer was prepared with an identical composition to the monobath developer prepared in Example 12, except for the sodium sulfide and potassium thiocyanate. A solution of 60 ml. of potassium thiocyanate (100 grams dissolved in 100 ml. of water to make up 154 ml. of solution), and 20 ml. of sodium sulfide (0.1 molar solution) 'was made up, and enough Water was added to make up to 2 liters. Then 400 ml. of sodium hydroxide (12 grams dissolved in sufficient water to make up 100 ml. of solution) were added to the solution.

A light-sensitive photographic lithographic film as described in Example 1 was exposed at a distance of 24 inches for 20 seconds to a #2 General Electric Photofiood lamp operated at 17 volts. The exposure was to a positive having a density of 1.4. The exposed film was physically divided in half. Both halves of the strip were developed for one minute in the developer solution and then washed with water for 30 seconds. The halves were then dipped for one minute in the alkaline solution of potassium thiocyanate and sodium sulfide and subsequently washed with water for 30 seconds. One-half was put back into the developer solution for one minute and then washed for three minutes. The other half was developed and washed the same Way but this second development and wash was carried out under actinic light. A high contrast, highly reflective, positive silver image was obtained in both halves on and/or in the antiabrasion surface coating of the emulsion layer. This developed film, that is, both halves thereof, constituted a printing plate. After several successive treatments with the acetic acid, ink, and cleaner, as described in Example 3, several positive copies were obtained from both halves.

EXAMPLE 14 A solution was prepared as follows:

Potassium iodide (0.5 molar solution), ml. Ethanol to make up to 100 ml.

A rubber stamp was wetted on the printing surface with the above solution. The wetted rubber stamp was pressed against the emulsion side of a light-sensitive photographic lithographic film as described in Example 1. The film was immersed in a developer identical to the one described in Example 1 for one minute, washed with water for three minutes and dried. A high contrast, highly-reflective,

negative silver image similar to the type of positive silver surface images obtained in Examples 1 through 13, was obtained on and/or in the antiabrasion surface coating of the emulsion layer. The potassium iodide functioned as a fogging agent similar in its effect to light, thereby preventing the formation of the silver image through silver transfer development in those areas where the potassium iodide was placed on the antiabrasion coating. This technique allowed a negative silver image to be formed. Several negative copies were obtained when the strip was used as a printing plate. This example demonstrates another use of the broad principle of using silver transfer development to obtain a printing plate.

EXAMPLE 15 A solution was prepared as follows:

Sodium sulfide (0.1 molar solution), 5 ml. Ethanol to make up to 100 ml.

A rubber stamp was wettedlon the printing surface with the above solution. The wetted rubber stamp was pressed against the emulsion side of a light-sensitive photographic lithographic film as described in Example 1.

A developer solution was prepared as follows:

Water ml.. 1600 Sodium sulfite (anhydrous) gm 160 2,4-diaminophenol (reagent grade) gm 36 Boric acid (H BO gm 11 6-nitrobenzimidazole nitrate (one gram dissolved in sufficient ethanol to make up 100 m1. of solution) ml Potassium thiocyanate grams dissolved in 100 ml. water to make up 154 ml. of solution) ml. 30

The film was given a fogging exposure, that is, not to a negative, for 20 seconds using a #2 General Electric Photofiood lamp at a distance of 25 inches operated at 20 volts. The film was immersed in the above developer solution for one minute, washed with water for three minutes, and dried. A high contrast, highly-reflective, positive silver image, similar to the positive silver surface images obtained in Examples 1 through 13, was obtained on and/or in the antiabrasion surface coating of the emulsion layer. As there was no nucleating agent in the developer, the silver surface image formed only where the nucleating agent had been introduced via the stamping of the film. Several positive copies were obtained when the strip was used as a printing plate, as in Example 3.

EXAMPLE 16 A light-sensitive photographic lithographic film as described in Example 1 was given a fogging exposure, that is, not to a negative, for 20 seconds utilizing a #2 General Electric Photoflood lamp at a distance of 25 inches operated at 20 volts. A rubber stamp was wetted on the printing surface with a solution of sodium sulfide in ethanol which was identical in composition to the solution described in Example 15. The wetted rubber stamp was pressed against the emulsion side of the film. The film was immersed in a developer solution which was identical to the developer solution described in Example 15 for one minute. The film was washed with water for three minutes and dried. A high contrast, highly-reflective, positive silver image, similar to the positive silver surface images obtained in Examples 1 through 13, was obtained on and/or in the antiabrasion surface coating of the emulsion layer. As there was no nucleating agent in the developer the silver surface image formed only where the nucleating agent had been introduced via the stamping of the film. Several positive copies were obtained when the strip was used as a printing plate, as in Example 3.

1 1 EXAMPLE 17 A developer solution was prepared as follows:

Water ml 1600 Sodium sulfite (anhydrous) gm 160 2,4-diaminophenol (reagent grade) gm 36 Boric acid (H BO gm l1- 6-nitrobenzimidazole nitrate (one gram dissolved in sufiicient ethanol to make up 100 ml. of solu- I tion) ml 80 Potassium thiocyanate (100 grams dissolved in 100 ml. water to make up 154 ml. of solution) ml 30 Potassium iodide (0.5 molar solution) ml 10 A rubber stamp was wetted on the printing surface with a solution of sodium sulfide in ethanol which was identical in composition to the solution described in Example 15. The Wetted rubber stamp was pressed against the emulsion side of a light-sensitive photographic film of lithographic type, as described in Example 1. The film was immersed in the monobath developer solution for one minute, washed with water for three minutes, and dried. A high contrast highly reflective, positive silver image, similar to the positive silver surface images obtained in Examples 1 through 13, was obtained on and/or in the antiabrasion surface coating of the emulsion layer. As there was no nucleating agent in the developer, the silver surface image formed only where the nucleating agent had been introduced via the stamping of the film. The potassium iodide is a fogging agent. Several positive copies were obtained when the strip was used as a printing plate.

EXAMPLE 18 The first bath solution of a developer consisting of solutions A and B was prepared as follows:

Solution A- Water (distilled) "mi... 3000 1-phenyl-3-pyrazolidone g 4 Ascorbic acid g 40 Sodium carbonate (anhydrous) g 80 Sodium hydroxide (10 grams dissolved in sufficient water to make up 100 ml. of solution) ml... 20 Water to make up to 4000 ml.

The second bath solution was prepared as follows:

Solution B- Water (distilled) ml 2600 Sodium sulfite (anhydrous) g 400 Hydroquinone g 8 1-phenyl-3-pyrazolidone g 0.5 Boric acid (H BO g 11 Sodium hydroxide (10 grams dissolved in sufficient water to make up 100 ml. of solution) ml 20 Sodium sulfide (0.1 molar solution) ml 20 Water to make up to 3000 ml. Sodium hydroxide (3.0 normal solution) ml 190 A light-sensitive photographic film was exposed at a distance of 26 inches for 10 seconds to a No. 2 General Electric Photoflood lamp operated at 40 volts A.C. Exposure was to a positive having a density greater than four. The film was comprised of a silver chloride emulsion containing 47 grams of gelatin per mole of silver chloride, overcoated with a clear hardened gelatin layer, and a thick cellulose triacetate base. The exposed film was immersed in solution A for 30 seconds, washed in water for 10 minutes, immersed in solution B for two minutes. A five-minute wash with water followed the second immersion. A highly reflective, positive, silver image was obtained on and/ or in the antiabrasion surface coating of the emulsion layer. This developed film constituted a printing plate. After several successive treatments with the aqueous acetic acid and ink step, and the cleaning step, as described in Example 3, several positive copies were obtained.

EXAMPLE 19 The first bath solution of the two-bath developer was the same as the first bath described in Example 6. The second bath solution was the same as the second bath, as described in Example 6.

A photographic film of the lithographic type was exposed at a distance of 24 inches for 20 seconds to a No. 2 General Electric Photoflood lamp operated at 17 volts A.C. Exposure was to a positive having a density of 1.4. The film was comprised of a high contrast silver chloride/ silver bromide emulsion, in which the silver salt contained 30 mole percent silver bromide and 70 mole percent silver chloride, and which contained 50 grams of gelatin per mole of silver halide, and a polyester base. The film did not have an antiabrasion layer. The exposed film was immersed for one minute in the first bath and washed for 15 seconds with water; immersed for 30 seconds in the second bath and washed for 15 seconds with water; immersed again for one minute in the first bath and washed for three minutes with water. A high contrast, highly reflective, positive silver image was obtained on and/or in the surface of the emulsion layer. This developed film constituted a printing plate. Several positive copies were obtained when the film was used as a printing plate.

As already mentioned, a two-bath developer may be used. The same set of agents may be used in both developer baths, or two different sets of agents can be utilized, or a single agent may be used in both developer baths. When a two-bath developer is used, the nucleating agent and the silver halide solvent are normally placed in the second bath. The first bath should contain no mercaptantype antifogging agent and minimal amounts of potassium bromide. The nucleating agent may be placed in the first bath but for optimum results the silver halide solvent should be restricted to the second bath. The above discussion also applies when a single-agent developer is used in the first bath in conjunction with a two-agent developer in the second bath. In effect, a two-bath developer can be arranged by starting with a two-agent developer to which, after the first stage of development is accomplished, is added the nucleating agent and silver halide solvent. If a single-agent developer is used first, another appropriate developing agent can be added with the silver halide solvent and nucleating agent. Or, if a two-agent developer is used first, the nucleating agent can be added at the start, and then, after that stage of development is accomplished, the silver halide solvent can be added. Or, if a single agent developer is used initially the nucleating agent can be added at the start, and after that stage of development, another appropriate developing agent and the silver halide solvent can be added. In all of the cases in which a monobath developer is used as a dual-bath developer, the starting solution should contain no mercaptan type antifogging agent and minimal amounts of potassium bromide. The foregoing discussion on the various combinations of monobath and two-bath developer utilization is in no way at all inclusive listing of possible combinations and was not meant to exclude operative combinations which were not specifically mentioned.

Although the light-sensitive element is usually transparent so that it can be exposed from either the front or back, an element with an opaque backing support, etc., can be exposed from the front and subsequently developed so that there is a necessary silver transfer to the unexposed surface region.

The preferred method of exposure is in a camera through the base or to the emulsion side using an imagereversing prism so that there is lateral image reversal; hence, in that manner a correctly oriented positive copy can be obtained when the light-sensitive element is ultimately used as a printing plate.

The organic colloid of the silver halide emulsion layer used in this invention is not especially critical and may be gelatin or, in place of gelatin, other natural or synthetic colloid binding agents. Such agents include waterpermeable or water-soluble polyvinyl alcohol and its derivatives, e.g., partially hydrolyzed polyvinyl acetates, polyvinyl ethers, and acetals containing a large number of extralinear CH CHOH groups; hydrolyzed interpolymers of vinyl acetate and unsaturated addition polymerizable compounds such as maleic anhydride, acrylic and methacrylic acid ethyl esters, and styrene. Suitable colloids of the last mentioned type are disclosed in US. Patents 2,276,322, 2,276,323 and 2,347,811. The useful polyvinyl acetals include polyvinyl acetaldehyde acetal polyvinyl butyraldehyde acetal and polyvinyl sodium-osulfobenzaldehyde acetal. Other useful colloid binding agents include poly-N-vinyllactams of Bolton, US. Patent 2,495,918, the oleophobic copolymers of N- acrylamidoalkylbetaines described in Shacklett, US. Patent 2,833,050, oleophobic cellulose ethers and esters, colloidal albumin, zein and polyacrylamide.

Similarly, the silver halide emulsion may be selected from well known emulsions containing silver chloride, or silver bromide, or mixtures of two or more compounds from the group consisting of silver chloride, silver bromide and silver iodide, as well as containing optical and chemical sensitizing agents, fog-stabilizing compounds, emulsion hardeners, plasticizing compounds, wetting agents, toners, and matting agents.

The film support for the emulsion layers used in the novel process may be any suitable transparent plastic. For example, the cellulosic supports, e.g., cellulose acetate, cellulose triacetate, cellulose mixed esters, etc. may be used. Polymerized vinyl compounds, e.g., copolymerized vinyl acetate and vinyl chloride, polystyrene, and polymerized acrylates may also be mentioned. The film formed from the polyesterification product of a dicarboxylic acid and a dihydric alcohol made according to the teachings of Alles, US. Patent 2,779,684, and the patents referred to in the specification of that patent. Other suitable supports are the polyethylene terephthalate/isophthalates of British Patent 766,290 and Canadian Patent 562,672 and those obtainable by condensing terephthalic acid and dimethyl terephthalate with propylene glycol, diethylene glycol, tetramethylene glycol or cyclohexane 1,4-dimethanol hexahydro-p-xylene alcohol. The films of Bauer et al. US. Patent 3,052,543, may also be used. The above polyester films are particularly suitable because of their dimensional stability.

Paper is another example of a suitable support for this novel process of obtaining the planographic printing form, if this paper is coated with a water-resisting and oleophilic layer, for example, with a hardened gelatin layer or superficially saponified cellulose acetate. Into such layers there may be incorporated matting agents such as titanium dioxide, silicon dioxide or barium sulfate, in varying quantities.

As the support for the planographic printing form, it is further possible to use plates consisting of metals, alloys, or metal oxide coated metal.

The light-sensitive element may or may not contain an antiabrasion layer, although its presence is preferred.

Besides immersing the light-sensitive element in the developer or developers solution. other methods of applying the solutions can be used such as dip roll, hopper, spray and the like so that a suflicient amount of solution is applied to the surface. It is probable that a highly viscous developer could be placed on the emulsion to provide semi-dry processing.

When making prior art printing plates, usually an ordinary negative is made and this is used for making a positive oleophilic image on the printing plate by contact exposure.

This invention eliminates the extra step of preparing the printing plate by contact exposure since the prior art step of making a negative is replaced herein by the direct preparation of the printing plate by, e.g., exposing directly in a camera. This constitutes a commercial advantage. Another advantage is that the process of the invention provides an economical and rapid way of making flexible positive printing plates. The process is versatile and dependable and does not require new photographic processing apparatus as the conventional apparatus can be used.

I claim:

1. process for making inked printing plates which comprises (a) forming by silver transfer development a silver surface image in an outer water-permeable hydrophilic organic integral colloid layer of a photographic film element having an exposed water-permeable organic colloid silver halide layer using an aqueous developer solution containing a silver halide solvent, a Water-soluble nucleating agent taken from the group consisting of water-soluble sulfides, selenides, and thiocyanates and thiourea in an amount of 50 to 3,000 mg. per liter, and hydroquinone or 2,4-diaminophenol or mixtures of either compound with 1 phenyl 3- pyrazolidone, l phenyl 4 methyl 3 pyrazolidone, or 1-methylamino-4-hydroxybenzene, and

(b) treating the surface of the image-bearing layer of said element (1) with an aqueous fountain solution, and (2) with a printing ink having an oleophilic binding agent, whereby said ink adheres to the areas of the surface that correspond to the silver image of said layer, and

(0) using said plates to print by lithography.

2. A process according to claim 1 wherein said colloid layer consitutes the outer layer.

3. A process according to claim 1 wherein the outer layer is an antiabrasion layer contiguous with the colloid layer.

4. A process according to claim 1 wherein said layer is a hardened water-permeable gelatin layer.

5. A process according to claim 1 wherein the surface image is a positive image.

6. A process according to claim 1 wherein the surface image is a negative image.

7. A process according to claim 1 wherein the exposed silver halide colloid layer is from imagewise exposure to actinic radiation.

8. A process according to claim 1 wherein the exposed silver halide colloid layer is from imagewise chemical exposure.

9. A process according to claim 1 wherein said fountain solution contains acetic acid.

10. A process according to claim 1 wherein said development is carried out in a single aqueous developer solution containing a silver halide solvent and a silver nucleating agent.

11. A process according to claim 1 wherein said development is carried out in two steps in two respective developer solutions, the silver halide solvent for silver transfer development being present in the second solution.

References Cited UNITED STATES PATENTS 3,335,005 8/1967 De Haes 9629 FOREIGN PATENTS 934,694 8/ 1963 Great Britain.

GEORGE F. LESMES, Primary Examiner I. P. BRAMMER, Assistant Examiner US. Cl. X.R. 9633, 66 

